My people asking me when they want to upgrade their Junos. Do I need to upgrade to the latest release? That’s very common question asking by many customers.
Personally (this is only in my mind), I’m a kind of person who do not like to upgrade the software. Especially in the big ISP environment when dealing with more than 100 routers.
Software upgrade in Junos is very simple things, you only needs to transfer your file via FTP, and do remote upgrade for just a couple of days. However, I will not recommend software upgrades unless you really needs some features which is maybe only supported in the next release.
Below is the list of what I usually consider before making recommendation for software upgrades.
1. You hit a bugs and has fixed in latest (maybe latest) version.
What can you do if you hit a bugs ? hehe… Nothing perfect in this world.
2. New hardware only supported in the specific software version.
In this case, there is no other choice rather than using supported software to these new hardware (i.e new module, interface card, etc).
3. You need new features that only available in the next release.
Network standards and RFC growth very fast. New technology standard will only supported in the latest release since the RFC is still new. You have no choice rather than using latest release. For the example (today) is ethernet-oam, nonstop-routing, etc.
4. Better software architectures.
Each release of software probably has unique architectures. Latest software somehow has better architectures than the previous one. For instance, memory distribution, mpls code, bgp code etc. You can take an advantages using latest release.
5. Software has reached EOL for a long time.
Btw, this is just my personal opinion and not represent any organization or company.
If you have another opinion, please let me know 
Let’s make a better world.
